There is a considerable need for improved diagnostic and
treatment algorithms to optimize successful patient outcomes after
orthopaedic shoulder infections as there has been a rapid increase
in the number of orthopaedic shoulder procedures performed in the
United States. Total shoulder arthroplasty rates are projected to
increase by more than 150 percent by the year 2020.

The accurate diagnosis of infection and identification of the
offending organisms continues to be a challenge, according to
Boyle, which is particularly true for Propionibacterium acnes (P.
acnes), one of the most common infecting organisms after
orthopaedic shoulder procedures.

Seeking More Accuracy in Diagnosing Infections

Diagnosing infection with P. acnes is a challenge due to the
indolent clinical presentation and unreliable nature of blood tests
and other common diagnostic tests for infection.

Diagnosing true infection with P. acnes relies largely on
intraoperative findings and the cultures that are taken in the
operating room at time of surgery. When those cultures from the
operating room do become positive for P. acnes, there
is controversy on distinguishing true infection from
contamination, Boyle says.

Hemolysis, defined as 2 mm of clearance around bacterial
colonies when cultured, has been noted in certain strains of P.
acnes and may be directly correlated with the bacteria’s
pathogenicity.

“The purpose of this study was to further evaluate
orthopaedic patients with and without hemolytic strains of P.
acnes,” Boyle says.

“We hypothesized that patients identified with hemolytic
strains of P. acnes would demonstrate a more prominent systemic
inflammatory response, greater antibiotic resistance and exhibit a
higher rate of definite clinical infection than non-hemolytic
strains of P. acnes,” she says.

Hemolysis Seen as Diagnostic Adjuvant

Indeed, the study found that hemolytic strains of P. acnes
demonstrate enhanced pathogenicity in their host and hemolysis
serves as a marker for true P. acnes infection.

Boyle says the significance of the study is that hemolysis can
be used as a diagnostic adjuvant for determining infection versus
contamination in P. acnes positive cultures.

The increased antibiotic resistance profiles seen in hemolytic
strains should be carefully considered when choosing antimicrobial
therapy for prophylactic and therapeutic courses of treatment, she
says.

Study Includes Retrospective Review of Patient Records

UB’s microbiology laboratory has been collecting and
storing P. acnes isolates since 2010. The basic science portion of
the study consisted of the research team plating the P. acnes
samples and evaluating for hemolysis as well as identifying
the various antibiotic resistance patterns.

The clinical aspect of the study involved retrospectively
reviewing the records of 31 patients who had a positive P. acnes
shoulder culture for demographics, preoperative labs,
intraoperative information, use of postoperative antibiotics and
clinical course, including determining whether these patients
required a return trip to the operating room for suspected
persistent infection.

Co-authors on the paper are:

Scott R. Nodzo, MD, an orthopaedic surgeon at Nellis Air Force
base in Las Vegas, Nevada. He graduated from the orthopaedic
surgery residency program at UB in 2015.

Diagnostic, Clinical Acumen Strong Focus of Program

Boyle says she had the opportunity to interview at many
orthopaedic surgery programs throughout the country, but she was
attracted to UB’s because she felt it offered one of the most
diverse and robust training programs with a solid foundation for
learning the principles of orthopaedics.

“This program has a strong focus not only on operative
experience and providing autonomy but also on developing a young
surgeon’s diagnostic and clinical acumen,” she
says.

Boyle notes the program’s leadership is very supportive of
resident research aspirations and novel ideas.

“I was given the opportunity to complete a three-month
research rotation in my PGY-2 year at the Hospital for Special
Surgery in New York City, where we evaluated current
treatment protocols, outcomes and economic burden of
orthopaedic infections after total knee and hip
replacement.”